A variety of different industrial ovens are used for a variety of different purposes. For example, industrial ovens are used to cure powder painted steel sheets and other parts. In this application, and all others, it is necessary to keep the work piece within a desired temperature range for a desired period of time to achieve the desired result. If the work piece temperature is allowed to climb too high the work piece will be damaged. If the work piece temperature is too low or inconstant the work piece may not be cured properly, or at least the time required to cure the work piece, and thus the flow of work product through the oven, is reduced. Maintaining optimum work piece temperatures is made more complicated for certain work pieces, such as metal articles, which act as heat sinks affecting the oven temperature, often significantly.
Convection ovens use a fan or fans to re-circulate air in the oven to enhance the heating characteristics of the oven. Movement of heated air over the work piece to be heated enhances oven operating efficiency. It has been found that oven operating efficiency can be increased by increasing air flow velocity over the work piece. One way to achieve this result is to increase air flow throughout the oven. However, the fan size and ductwork needed to provide the required air velocity throughout an oven is often expensive and inefficient.
As an alternative, attempts have been made to increase air velocity in an oven specifically through a heat transfer zone of the oven where the work piece is to be placed or through which the work piece is to be moved. For example, some ovens have an air supply duct located in the bottom of the oven with air nozzles that discharge air upward over the work piece being heated in the heat transfer zone of the oven. Other ovens have two air supply ducts, one located in the upper corner on each side of the oven. High velocity nozzles are used to blow air vertically downward along the oven walls where it is then turned upward over the work piece being heated in the heat transfer zone. This design has proven effective in maintaining uniformity of both oven air temperature, and air velocity, across the work piece. It helps to even out the temperature rise of the entire work piece and to minimize flutter of suspended work pieces due to uneven air velocities. An additional benefit is that the oven walls are kept hot, reducing the tendency for condensation to build up. The high velocity nozzles used in this application are designed to induce a venturi effect that draws in a significant amount of the air inside the oven chamber. The result is that the volume of air passing through the work piece is much higher than the capacity of the circulation fans. This enhances temperature uniformity and heat transfer as well as reduces the electrical energy consumption of the circulation fan motors. However, the use of high velocity air nozzles alone is limited in that it does not provide control of the quantity and direction of air flow through the oven.
What is desired, therefore, is an improved convection oven that employs turbo flow air nozzles for increasing air flow through the heat transfer zone of the oven and a method of using such an oven to heat work pieces.